1. Field of the Invention
The present invention relates to phenylenediamine derivatives and methods for using the same. In one particular aspect of the present invention, phenylenediamine derivatives of the present invention are used as an additive in chemically amplified photoresist films for increasing the energy latitude (EL) margin, and improving a contrast value and post exposure delay (PED) stability.
2. Description of the Background Art
Use of chemical amplification-type photoresists (i.e., photoresist compositions) is currently being investigated in photolithography processes to achieve a high sensitivity in minute image-formation on semiconductor devices. Such photoresists are generally prepared by blending a photoacid generator with a matrix resin polymer (i.e., photoresist polymer) having an acid labile group.
In a photolithography process for producing semiconductor devices, the resolution of an image depends on the wavelength of the light used. Thus, the shorter the wavelength, higher the resolution, i.e., shorter wavelengths allow smaller pattern formation.
In order to be useful in a photolithography process, a photoresist (PR) must have an excellent etching and heat resistance, and adhesiveness. Moreover, to reduce the cost of manufacturing semiconductor devices, a PR should be capable of being developed by a common developing solution, such as a 2.38 wt % aqueous tetramethylammonium hydroxide (TMAH) solution. These qualities are particularly important in photolithography processes utilizing a deep ultraviolet light source (i.e., short wavelength light source), including KrF (248 nm), ArF (193 nm) and EUV.
While it is difficult to synthesize a photoresist polymer that satisfies all of these requirements, a variety of photoresist polymers with improved etching resistance, adhesiveness and resolution have been developed. Unfortunately, however, most chemically-amplified photoresists currently available have a relatively short post exposure delay (PED) stability. In general, when there is delay between exposure of the photoresist to light and development of the exposed photoresist, acids that are generated on the exposed area are neutralized by amine compounds which may be present in the production atmosphere. Since the pattern formation depends on acids that are generated by the exposure, neutralization of acids by atmospheric amine compounds reduce, prevent or alter a pattern formation, e.g, a T-topping phenomenon may occur where the top portion of the pattern forms a T-shape.
In theory, one may overcome the aforementioned disadvantages by improving the photoresist polymer or by adding an additive to improve the PED stability of the photoresist composition. In the conventional art, various amine compounds, in particular amine compounds that are weakly basic and/or have bulky groups have been employed as an additive to increase the PED stability. However, most of these additives dissolve relatively equally well in the exposed and unexposed regions. In addition, most of these additives are relatively volatile liquids which escape into the atmosphere during the post exposure delay; therefore, photoresists containing these amine compounds have poor reproducibility. Furthermore, since these amine compounds are volatile, it is difficult to control the precise amount of these additives present in the photoresist during a photolithiography process.
Therefore, there is a need for a photoresist additive compound which overcomes the above-mentioned disadvantages.
It is therefore an object of the present invention to provide a photoresist additive compound which increases the PED stability of a photoresist.
It is also an object of the present invention to provide a photoresist additive compound which increases the energy latitude (EL) margin and improves the contrast value of the photoresist.
In order to achieve the above-described objectives, the present invention provides novel phenylenediamine derivatives. Without being bound by any theory, it is believed that phenylenediamine derivatives of the present invention improve PED stability of a photoresist by preventing or reducing the number of contacts between the acid that is generated on the exposed area and environmental amine compounds.